;; Make the window simpler
'("marmalade" . "http://marmalade-repo.org /packages/"))
'("melpa" . "http://melpa.milkbox.net/packages/"))
Unfortunately, the blackboard theme in the package manager is using the old color-theme package which has been made obsolete with Emacs 24. You should use the version ported to the new and improved theming mechanism.
Download that and put it in ~/.emacs.d/themes. Now you can set it up with:
(setq custom-theme-directory "~/.emacs.d/themes/")
(setq custom-safe-themes t)